He is much better out & out winger than any we have. Doing better proper winger job than any of our players: balance between attacking & defending, keeping wide, stretching play, beating his man, putting cross in, tracking opposition full back... Team can't stop Valencia from running through them on right wing. problem is his creativity suck so he is converted to a full back as his defensive work is still top notch. He's in 30s too. Doesn't look like player automatically decline physical at 30 like in video game. Perisic is not the forward to score 20+ goals, but he helped a lot in the build up. We're over-relying on Pogba especially toward the end of the season. He had to do everything. With Perisic to share the responsibilities, the team would improve, Pogba would improve. Yes we will still look at the players to put the ball into the net, but that was going to happen regardless. The more you say, the more I see that you seem not to watch Perisic at all. I know it's hard to judge a player, but IMO if I have to describe the Perisic the last season, he is the blend/ average of the young Robben & Darmien Duff. That's not top player but pretty good player that capable for a title challenging team in the right set up.
I will repeat again, until the official fee announce, all is up to speculation. If anything the more reliable source showed that we have been posturing to get a reasonable price. Even at 44mil like what you like to believe, the price will only get crazier with time. In case he lives up to the manager's expectation for like 2 seasons, that' good enough. Mourinho would go for winning the trophies. That's the expectation to be clear.